Techniques are disclosed, by which a plurality of flaps included in a wind pressure type shutter unit are positioned approximately in parallel to the direction of a passage so that the passage enters an open state and when reverse wind from an air outlet is caused by a fan failure, the flaps slightly inclined with respect to the direction of the passage receive the pressure of the reverse wind and close the passage.
Other techniques, by which a large number of shutter plates are coupled together by a coupling member and all of the shutter plates are caused to swing approximately concurrently, are disclosed.
Further, techniques are disclosed, by which three shutters are coupled together by a shutter coupling member and caused to perform opening and closing operations in the interlocking relationship with one another.
Japanese Laid-open Patent Publication No. 2011-231954, Japanese Unexamined Utility Model Registration Application Publication No. 6-78741, and Japanese Laid-open Patent Publication No. 8-338649 are examples of related art.